Decorator (DC01)

   1:  @decoratorFunction

   2:  class MyClass { /* ... */ }

   3:  

   4:  @decoratorFunction

   5:  function myMethod() { /* ... */ }

   6:  

   7:  @decoratorFunction

   8:  get myProperty() { /* ... */ }

Decorators are a form of metaprogramming in JavaScript. They provide a way to wrap additional functionality around existing code (classes, methods, accessors, properties, or parameters) without directly modifying the original code itself. Think of them as "decorators" that enhance or modify the behavior of the underlying code element. In essence, a decorator is a higher-order function that takes a target (the thing being decorated) and returns a modified version of that target or something that replaces it.

Decorators use the @ symbol followed by the decorator function's name, placed directly before the code element being decorated:

Decorator Types:

• • Class Decorators: Applied to classes. Can modify the class's constructor or prototype.
• • Method Decorators: Applied to methods. Can modify the method's behavior.
• • Accessor Decorators: Applied to getters or setters. Can modify how properties are accessed or set.
• • Property Decorators: Applied to properties. Can add metadata to properties.
• • Parameter Decorators: Applied to function parameters. Can provide information about or modify the parameter's behavior.

How Decorators Work, A decorator function takes the following arguments:

• • For class decorators: The constructor of the class.
• • For method/accessor/property decorators: A descriptor object for the method/accessor/property.
• • For parameter decorators: The target (object or class prototype), the property key (name of the method or property), and the parameter index.

The decorator function can then modify the target, descriptor, or return a new descriptor. This allows it to wrap additional logic around the original code.

Key Points to Remember:

• • Experimental Stage (But Standardizing): Decorators are now part of the JavaScript standard.
• • Tooling Support: IDE support for decorators is improving but might still be limited.
• • Order of Execution: Decorators are applied from bottom to top (innermost to outermost).
• • Clarity vs. Magic: Use decorators judiciously. Overuse can make code harder to understand.

Decorator context:

ES6 context:

Comments ( )